Aspirin Seen Aiding Colorectal Cancer Patients
By RONI CARYN RABIN
Published: August 11, 2009
It has long been known that people who took aspirin regularly were less likely to develop tumors of the colon, and now a study has found that even after a diagnosis of colorectal cancer, patients who took aspirin had a much better chance of surviving than non-users.
The improvements in outcomes were striking. Patients with colorectal cancer who regularly used aspirin before and after a diagnosis were almost one-third less likely to die of the disease than non-users. Patients who initiated aspirin use only after a diagnosis did even better and had half the risk of dying from the cancer, possibly because of differences in their tumors. The patients were all being treated for nonmetastatic, or localized, cancers, and were followed for almost 12 years on average.
The study, written by researchers from Harvard Medical School, Massachusetts General Hospital and the Dana-Farber Cancer Institute, is being published in this week’s Journal of the American Medical Association. An abstract is available online.
“This is a remarkable breakthrough ― for a pill that costs a penny,” said Dr. Alfred I. Neugut, a colon cancer expert at Columbia University’s College of Physicians and Surgeons, who was not involved in the research but wrote an editorial accompanying the article. “Aspirin is not a benign drug, so I can’t recommend purely on the basis of this study that someone should take aspirin, but it’s pretty darn close.”
The paper was based on an observational study that followed 1,279 men and women with nonmetastatic colorectal cancer, and thus was not the kind of randomized controlled clinical trial considered the gold standard for determining the course of treatment in medicine.
What lends credence to the results is that doctors understand the biological mechanism by which aspirin may prevent the growth and slow the spread of colon cancer, since most colorectal cancer tumors are positive for cyclooxygenase-2, or COX-2, an enzyme that is not expressed in a healthy colon but flares up under certain circumstances, and aspirin is a COX-2 inhibitor.
As part of the new study, the researchers analyzed the tumors that were available from a subgroup of 459 patients, and discovered that those whose tumors overexpressed the COX-2 enzyme were particularly responsive to aspirin use. Among those patients, regular aspirin use was associated with a 61 percent drop in death rate compared with patients who used aspirin but had tumors that did not express COX-2 or had only weak expression.
Aspirin Use and Survival After Diagnosis of Colorectal Cancer
Andrew T. Chan, MD, MPH; Shuji Ogino, MD, PhD; Charles S. Fuchs, MD, MPH
Context Aspirin reduces risk of colorectal neoplasia in randomized trials and inhibits tumor growth and metastases in animal models. However, the influence of aspirin on survival after diagnosis of colorectal cancer is unknown.
Objective To examine the association between aspirin use after colorectal cancer diagnosis on colorectal cancer--specific and overall survival.
Design, Setting, and Participants Prospective cohort study of 1279 men and women diagnosed with stage I, II, or III colorectal cancer. Participants were enrolled in 2 nationwide health professional cohorts in 1980 and 1986 prior to diagnosis and followed up through June 1, 2008.
Main Outcome Measure Colorectal cancer--specific and overall mortality.
Results After a median follow-up of 11.8 years, there were 193 total deaths (35%) and 81 colorectal cancer--specific deaths (15%) among 549 participants who regularly used aspirin after colorectal cancer diagnosis, compared with 287 total deaths (39%) and 141 colorectal cancer--specific deaths (19%) among 730 participants who did not use aspirin. Compared with nonusers, participants who regularly used aspirin after diagnosis experienced a multivariate hazard ratio (HR) for colorectal cancer--specific mortality of 0.71 (95% confidence interval [CI], 0.53-0.95) and for overall mortality of 0.79 (95% CI, 0.65-0.97). Among 719 participants who did not use aspirin before diagnosis, aspirin use initiated after diagnosis was associated with a multivariate HR for colorectal cancer--specific mortality of 0.53 (95% CI, 0.33-0.86). Among 459 participants with colorectal cancers that were accessible for immunohistochemical assessment, the effect of aspirin differed significantly according to cyclooxygenase 2 (COX-2) expression (P for interaction = .04). Regular aspirin use after diagnosis was associated with a lower risk of colorectal cancer--specific mortality among participants in whom primary tumors overexpressed COX-2 (multivariate HR, 0.39; 95% CI, 0.20-0.76), whereas aspirin use was not associated with lower risk among those with primary tumors with weak or absent expression (multivariate HR, 1.22; 95% CI, 0.36-4.18).
Conclusion Regular aspirin use after the diagnosis of colorectal cancer is associated with lower risk of colorectal cancer--specific and overall mortality, especially among individuals with tumors that overexpress COX-2.
Author Affiliations: Gastrointestinal Unit, Massachusetts General Hospital and Harvard Medical School (Dr Chan); Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, and Department of Epidemiology, Harvard School of Public Health (Dr Ogino); Department of Medical Oncology, Dana-Farber Cancer Institute (Drs Ogino and Fuchs); Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School (Drs Chan and Fuchs) Boston, Massachusetts.
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